Drill stabilizer tool



Jan. 7, 1969 o. E. OWENS DRILL STABILIZER TOOL Original Filed Oct. 21., 1966 FIG. 3.

INV ENT OR DEWEY E. OWENS BY MKWQA. ATTORNEY United States Patent 3,420,323 DRILL STABILIZER TOOL Dewey E. Owens, Lafayette, La., assignor to Land and Marine Rental Company, Houston, Tex., a corporation of Delaware Continuation of application Ser. No. 588,403, Oct. 21,

1966. This application Feb. 23, 1967, Ser. No. 617,929

U.S. Cl. 175323 19 Claims Int. Cl. E21b 17/046; 17/10 ABSTRACT OF THE DISCLOSURE A blade stabilizer suitable for interconnection in a well drilling string and having a greatly reduced tendency for balling and sticking in down hole drilling operations is provided with a nonadhering plastic covering, e.g., a tetrafiuoroethylene polymer, covering those nonbearing portions of the stabilizer body between the blades. The plastic covering may be in sheet form secured in undercuts at the base of the stabilizer blades.

Cross reference to related applications The instant application is a continuation of application Ser. No. 588,403 filed Oct. 21, 1966, now abandoned, in the name of Dewey E. Owens as inventor.

Background of the invention This invention relates generally to well drilling operations and more particularly to an improved stabilizer tool adapted to be periodically disposed throughout the drill pipe string for maintaining the drill string centrally positioned in the borehole or casing and for performing reaming operations as desired.

The novel tool of this invention will be recognized by those skilled in the art as possessing the outer configuration of a blade stabilizer. However, as is known in the art, these tools are also utilized to perform reaming functions, and accordingly, reference may be made herein to this novel tool as a reaming and a stabilizing tool.

The device of the instant invention provides an improved reamer and stabilizer offering decided advantages when utilized as a component of the drill pipe string disposed either within the well borehole or the well casing. The problem often encountered when using the presently known types of stabilizers is the sticking or balling of the drill string within bore or casing due to the insistent buildup of either drill cuttings, mud, cement, or the like about the stabilizer blades. The blade stabilizer conventionally includes a pipelike body having outwardly extending blades outwardly facing bearing surfaces. These bearing surfaces are the outermost surfaces on the stabilizer and are of a diameter slightly less than the casing or bore diameter. Hence, these bearing surfaces will be first to contact the casing or borehole wall to stabilize the drill string. Of course, during drilling, these blades which are typically dressed with hard facing material on their outer bearing surfaces will also function as reamers.

It has been found that ordinary stabilizers tend to carry a buildup of mud, drill cuttings, and like drilling debris between the blades during drilling. This balling effect clogs the casing against drilling fluid flow and also can cause the stabilizer to become stuck thus freezing the drill string.

Summary of the invention There is accordingly provided by this invention a novel stabilizing and reaming tool which may be employed in down hole operations under conditions tending to result in material buildup around the blades, having a nonadhering surface provided by a lubricious plastic covering 3,420,323 Patented Jan. 7, 1969 having nonadherent properties around the stabilizer body between the blades. A tetrafluoroethylene polymer is highly preferred as the material for this covering since these polymers are extremely resistant to chemical attack qualities of nonadherence. Other polymers may also be employed for this plastic covering such as other fluorocarbon polymers, the polyamides or nylons or the like.

The placement of such a nonadhering covering on the stabilizer body between the blades precludes material buildup between the blades as a result of the scraping or reaming action of the blades. It has been found that mud and other drilling debris does not find a secure base on this plastic covering and is readily removed from the region of the stabilizer by circulating fluids, and by gravity thus virtually precluding the problem of balling which has heretofore been a problem with blade stabilizers.

Brief description 07" the drawings The instant invention will be more particularly understood with reference to the accompanying drawings which illustrate the instant invention in specific embodiments.

FIGURE 1 is a side elevation, partly in section, of the present invention with portions broken away for clarity.

FIGURE 2 is a side elevation, partly in section, of a modification of the instant invention with portions broken away for clarity.

FIGURE 3 is a sectional view taken along line 33 of FIGURE 1.

Description of the preferred embodiments Referring to the drawings, particularly FIGURE 1, it will be seen that the present invention comprises a stabilizer tool generally designated 1, and includes a reamer body 2 on which blades 8 are mounted, the said body being provided at the opposite ends thereof with an upper pipe section 3 and a lower pipe section 4. The stabilizer tool 1 is intended to be utilized at periodc points throughout the drill pipe string and will be attached therein to the axially adjacent drill pipe by means of the conventional box end portion 5 and pin end portion 6 formed at the opposite ends of the tool 1.

The cylindrical peripheral surface 7 of the reamer body 2 is undersized, i.e., of reduced diameter, with respect to the adjacent cylindrical portions of the upper and lower pipe sections 3 and 4, respectively, as will be most clearly seen in the right-hand portion of FIGURE 1. The purpose of the reduced diameter base portion 7 will become 7 apparent hereinafter. Extending radially outward from the base portion 7 of the reamer body 2 is a plurality of reamer cutting blades 8 which extend longitudinally along the reamer body 2 a distance less than the axial length of the reduced diameter portion 7. The blades 8 may be formed integral with the reamer body as by casting or milling or may be welded onto the reamer body 2, which is more common among conventional stabilizers.

The outer surfaces of the reamer blades 8 upon rotation define a cylinder of rotation concentric with the surface 7 of the reamer body while the ends of these blades are disposed in an inclined relationship to provide an upper inclined blade surface 9 and lower inclined blade surface 10 at the ends of each of the blades. The outer surfaces 8a of blades 8 are preferably dressed with a hard facing material since these surfaces are the bearing surfaces which contact or bear against the borehole or casing wall to center the drill string and to ream when the tool is down hole. The hard facing preferably extends onto inclined surfaces 9 and 10 at the blade extremities. Tungsten carbide or a like hard facing material may be employed to dress these outwardly facing bearing surfaces on the blades.

The nonadhering lubricious plastic material is secured to the nonbearing surfaces of the reamer body between the blades. Although toughness is a desired characteristic in selection of the plastic, this plastic material is not capable of withstanding the wear which would be encountered by the bearing surfaces. At the point where the reduced diameter base portion 7 joins the lower pipe section 4, an undercut or V-shaped ring 11 is provided while the opposite end of the reamer body 2 adjacent the upper pipe section 3 is formed with a straight radial shoulder 12 as will be seen in FIGURE 1 of the drawing. In order to provide for a secure locking of the plastic material which is to be applied about the reamer body 2, each of the blades 8 includes a lateral recess 13 extending from a point spaced from the outer bearing surface 8a at the base of each blade. This undercut area, or recess, is extended beneath each end of the incline blade surfaces 9 and 10 to provide a blade undercut area 14 at these points. Thus, it will be seen that a recess or undercut is provided not only along the lateral surfaces of the webs of each of the blades but also at the ends thereof.

Disposed about the reduced diameter portion 7 of the reamer body 2 is a layer or sleeve of suitable plastic material having a low coefiicient of friction and extending from the straight shoulder 12 at the upper end of the reamer body to the undercut ring 11 at the lower end of the body. The plastic material may be in the form of sheets sized to fit between the blades and extend from shoulder 12 to undercut ring 11 and also extending around the top and bottom recesses of the blades. The sheets may be secured to the body in any suitable manner as will be discussed below.

In the area between the ends of the inclined blade surfaces 9 and 10 and the adjacent upper and lower pipe sections 3 and 4, it will be seen that the plastic 15 forms a sleeve or sheath which completely encircles the reamer body 2. The plastic is securely anchored at the lower end within the undercut ring 11 which is the area of the tool 1 subjected to the most abuse. The plastic also overlies the body surfaces 7 between each of the reamer blades 8 and extends to fill the recesses 13 on either side of each blade and also is disposed beneath the undercut areas 14 at both ends of each blade in such a manner that the entire plastic sleeve 15 will be securely keyed or anchored to the body and blades of the tool.

The plastic materials which can be employed to provide the nonadhering sheating to the body portion 7 include those lubricious nonadhering organic polymers such as the fluorocarbon polymers, specifically tetrafluoroethylene polymer, commonly sold under the trademark Teflon, and polyamide polymers or nylons such as polyhexamethylene adipamide or the like. The plastic sheating material must be also capable of withstanding the corrosive effects of materials encountered down hole and must possess a measure of toughness since although the plastic is not a bearing surface, it will encounter abrasive effects from drilling debris and the like. The fluorocarbon polymers and the polyamides possess this toughness as well as the nonadhering properties. Tetrafluoroethylene polymer is most eminently preferred for its singular properties of nonadhesion, its toughness and its resistance to chemical corrosion.

The thickness of plastic employed to sheath the body portion 7 will depend upon the toughness of the particular plastic to be employed and the severity of conditions under which operation of the stabilizer is anticipated. Typically it has been found sufficient to employ a sheath of plastic sheet one-sixteenth to one-eighth inch in thickness when using tetrafiuoroethylene polymer as the sheath material. The thickness of the plastic sheating preferably corresponds to the height of shoulder 12 and undercut 11 so that when secured in position, the plastic surface is flush with the surface of the adjoining pipe sections.

Any one of several means may be utilized to secure the plastic material to the stabilizer body. One preferred manner, when dealing with tetrafluoroethylene polymer, is to etch the inner surface of the polymer sheet with, for

example, a fused alkali metal, to provide an improved bonding surface. Also, that portion of the stabilizer to which the plastic will be secured is also surface roughened, for example, by sandblasting or the like. The plastic is then bonded to the body in region 7 by a suitable adhesive 16 such as an epoxy cement and is held in place on the stabilizer until the adhesive bond is completed.

The present invention may be utilized to provide a stabilizer tool having a plurality of helically disposed blades 8' as illustrated in the reamer tool In shown in FIGURE 2 of the drawing. The reamer body 2 is formed in the same manner in this embodiment as described in connection with the previous form of the invention and likewise each of the reamer blades 8' is provided with the lateral undercut portions or recesses 13 as well as the blade undercut areas 14 at either end of each blade beneath the incline surfaces thereof.

It is pointed out that the plastic sheathing 15 may be secured to the body of the stabilizer employing methods other than that illustrated in the drawings and discussed above. For example, the sheathing need not be keyed into undercut areas of the blades but could be secured to abut with the perpendicular Wall of the blades. Alternatively if the lateral edges of the blades slope upwardly to the bearing surface, the sheathing can be formed with a feathered edge to fit between the blades and produce a smooth meeting of blade and plastic. Further, it is pointed out that the plastic material may be formed directly onto the reamer body in region 7 as by casting or using other depositing processes known to those familiar with the polymer art.

It should be appreciated that tools of the type of this invention are often required to operate down hole amidst abrasive debris in a fluid medium under pressure often in the range of several thousand pounds. Thus the bonding of the sheath to the stabilizer body whether accomplished by any of the above methods must be capable of holding up under these conditions. The keyseating bonding arrangement of the drawings utilizes undercuts under the blades to protect the joinder between the plastic and the stabilizer body. Hence this preferred method affords greatest protection to the plastic when secured in place.

From the foregoing description, it will be seen that an improved stabilizing and reaming tool is provided having the advantages of an all-metal tool and which eliminates the primary disadvantage of prior metal tools by providing a plastic sheath low coefiicient of friction which is securely anchored to the body between the blades and overlies those areas of the reamer which heretofore were subject to clogging due to the accumulation of foreign materials during well drilling operations.

What is claimed is:

1. In a stabilizer suitable for interconnection in a drill string, said stabilizer including a metallic tubular body portion having a plurality of blades with outwardly facing, wear-resistant bearing surfaces extending outwardly from said body, the improvement in combination therewith comprising a covering of a lubricious nonadherent plastic on the nonbearing surfaces between said blades to prevent material buildup around said blades during drilling.

2. The stabilizer of claim 1 wherein said plastic is a fluorocarbon polymer.

3. The stabilizer of claim 2 wherein said plastic is a tetrafluoroethylene polymer.

4. The stabilizer of claim 1 wherein said plastic is a polyamide.

5. The stabilizer of claim 1 wherein said plastic covers said nonbearing surfaces and comprises a sheet of polymer secured in undercuts beneath said blades.

6. A drill stabilizer suitable for interconnection in a drill string which comprises:

a tubular body portion,

a plurality of blades secured to and extending outwardly of said body portion, said blades having outwardly facing bearing surfaces dressed with hard facing material, and

a covering of lubricious nonadhering plastic on the nonbearing surfaces between said blades to prevent material buildup around said blades during drilling.

7. The drill stabilizer of claim 6 wherein said plastic is a fluorocarbon polymer.

8. The drill stabilizer of claim 7 wherein said plastic is a tetrafluoroethylene polymer.

9. The drill collar of claim 6 wherein said covering comprises a tetrafluoroethylene polymer sheet adhered to the nonbearing surfaces of said body portion and secured in undercuts beneath said blades.

10. A drill stabilizer suitable for interconnection in a drill string which comprises:

a tubular member having a reduced diameter medial body portion and upper and lower pipe sections above and below said reduced diameter medial portion,

a plurality of blades having outwardly facing bearing surfaces extending outwardly from said reduced diameter portion, said blades having undercuts along the bases thereof at the surface of said reduced diameter portion,

a covering .of lubricious nonadhering plastic over said reduced diameter portion secured in said undercuts.

11. The stabilizer of claim 10 wherein the outer surface of said covering is flush with the surface of said upper and lower pipe sections.

12. The stabilizer of claim 10 wherein said plastic is a tetrafluoroethylene polymer.

13. The stabilizer of claim 12 wherein said tetrafiuoroethylene polymer covering is in the form of sheet material secured to the reduced diameter portion by an adhesive.

14. The stabilizer of claim 13 wherein the inner surface of said tetrafluoroethylene sheet is chemically etched and said medial body portion is surface roughened to improve the adhesion therebetween.

15. The stabilizer of claim 13 wherein said adhesive is an epoxy cement.

16. The stabilizer of claim 13 including a straight shoulder at one end of said reduced diameter section and an undercut ring at the other end thereof whereby said sheet abuts completely said shoulder and said ring.

17. The stabilizer of claim 10 wherein said blades are straight and extend longitudinally along said reduced diameter section.

18. The stabilizer of claim 10 wherein said blades'are curved and extend helically around said reduced diameter section.

19. The stabilizer of claim 10 wherein said undercut areas at the bases of said blades extend outwardly from the body along the sides of said blades to a point on said blades spaced from the outer bearing surfaces of said blades and said plastic is secured in said undecut area to cover a portion of the sides of said blades.

References Cited UNITED STATES PATENTS 3,049,382 8/1962 Ell.

3,103,391 9/1963 Leathers.

3,231,019 1/1966 Clay et al 166242 3,343,890 9/1967 Homer.

JAMES A. LEPPINK, Primary Examiner.

US. Cl. X.R. 175-406; 3084 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,420 ,323 January 7 1969 Dewey E. Owens It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

line 4, after "attack" insert and have a low Column 2 coefficient of friction exhibiting excellent line 37, "periodc" should read periodic Column 6, line 21, "undecut" should read undercut Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

Edward M Fletcher, J r.

Commissioner of Patents Attcsting Officer WILLIAM E. SCHUYLER, JR. 

